Solid grain caseless ammunition propellant

ABSTRACT

The specification discloses caseless ammunition and solid propellant grains therefor in which there are provided a plurality of separate perforations extending rearwardly from the front end of the grain and substantially parallel to its longitudinal axis, and terminating short of the rear end of the grain. Ignition of the grain causes burning to develop through the perforations such that the projectile is propelled forwardly through the gun barrel leaving the grain in the chamber.

Unite States atent Paul et al.

[ 1 Sept. 5, 1972 [54] SOLID GRAIN CASELESS AMMUNITION PROPELLANT [72]-Inventors: Ben E. Paul, Costa Mesa; Ival L. Olmstead, Fountain Valley,both of I Calif.

[73] Assignee: Aerojet-General Corporation, El

Monte, Calif.

[22] Filed: July 31, 1969 [21] Appl. No.: 846,429

[52] U.S. Cl. ..102/38, 102/40, 102/45,

102/DlG. l

[51] Int. Cl ..F42b 5/18 [58] Field of Search ..l02/38 C0, 40, 43

[56] References Cited! UNITED STATES PATENTS 430,229 6/ 1 890 Garland102/40 540,327 6/1895 Maxim ..102/40 695,809 3/1902 Hawk ..102/DIG. 1

2,632,391 3/ 1953 Kintzinger 102/43 P 3,345,945 10/ 1967 Quinlan et al...102/38 3,482,516 12/ 1969 Farmer et a1. ..102/38 694,295 2/ 1902 Maxim..l02/D1G. l

FOREIGN PATENTS OR APPLICATIONS 14,678 1889 Great Britain 102/38 488,8191938 Great Britain ..l02/42 Primary Examiner-Robert F. StahlAttorney-Edward O, Ansell and D. Gordon Angus [57] ABSTRACT Thespecification discloses caseless ammunition and solid propellant grainstherefor in which there are provided a plurality of separateperforations extending rearwardly from the front end of the grain andsubstantially parallel to its longitudinal axis, and terminating shortof the rear end of the grain. Ignition of the grain causes burning todevelop through the perforations such that the projectile is propelledforwardly through the gun barrel leaving the grain in the chamber.

6Claims,8DrawingFigures msminw Si n SHEET 1 OF 3 km \N PKTENTED SEP 5I973 3.688.697

- sum 2 BF 3 INVENTOR. 55v 5 PA UL Jl/AL .4. OLMSTEAD SOLID GRAINCASELESS AMMUNITION PROPELLANT This invention relates to solid graintype caseless ammunition and particularly to a propellant grain thereforand to an organization of the grain with a projectile and an igniter.

Caseless ammunition has heretofore been known, in which a projectile isset in front of the propellant, or telescoped into the propellant grain.In such prior caseless ammunition arrangements, the propellant has beenignited, causing the usual rapid burning with attendant formation ofgases which serve to propel the projectile forwardly.

An undesirable factor in the use of such systems has been that thepropellant would be propelled forwardly along with the projectilethrough the gun barrel thus adding undesirable mass to the projectile.

An object of the present invention is to provide a caseless ammunitionsystem in the operation of which the grain is maintained in the chamberof the gun while the projectile is propelled forwardly.

In accordance with the present invention, there is provided a solidpropellant grain to which the projectile is to be fitted, as at thefront end of the projectile, or alternatively by telescoping theprojectile into the propellant grain. A feature of the arrangement isthe provision of a plurality of separated, axially elongatedperforations extending substantially parallel to the iongitudinal axisof the grain and opening onto the forward end of the grain. There isalso provided ignition means which initiates burning of the grain andcauses the burning to enter the perforations at their forward ends andburn along the internal surfaces thereof. Thus, in the individualperforations, burning occurs in a generally radial direction relative tothe longitudinal axis of each perforation.

As a result of this form of burning initiation and grain burning, thepropellant is constrained in the chamber of the gun while the projectileis expelled forwardly. This constitutes a great advantage overarrangements wherein burning is commenced at the rearend instead of atthe forward end of the grain. When burning starts at. the rear, thepropellant tends to be propelled with the projectile.

Features reside in arrangements whereby the projectile is expelled fromthe grain and the grain is ignited.

The foregoing and other features of the invention will be betterunderstood from the following detailed description and the accompanyingdrawing of which:

FIG. 1 is a longitudinal cross-section view of caseless ammunitionaccording to the present invention, taken at line l--l ofFIG. 2;

FIG. 2 is a cross-section view taken at line 2-2 of FIG. 1;

FIG. 3 to FIG. 7 show other embodiments of caseless ammunition accordingto this invention wherein the projectile is fully telescoped by thepropellant; and

FIG. 8 shows another embodiment of caseless ammunition according to thisinvention in which the projectile is not fully telescoped by thepropellant.

Referring to FIGS. 1 and 2 of the drawings, there is shown a form ofcaseless ammunition comprising a projectile 10 such as a bullet, havinga forward head 11 fitted into a rear part 12 of the projectile by thefitting of an axially located cylindrical end 13 into a bore 14 of therear portion 12. This rear portion comprises a cylindrical member 15with a forward flange 16 which meets the head 11 of the bullet near itscircumferential area and is provided with a lip 17 in a manner to fitwith the forward end of a propellant grain.

The propellant grain 18 is in the form of a cylinder 19 of solidpropellant, the outer diameter of which is dimensioned to fit thechamber of the gun and the forward end 20 of which tapers inwardlytoward the axis to meet the smaller diameter projectile. The forward endof the grain has a cylindrical opening 22 along the central longitudinalaxis of the grain and extending from the forward end thereof for adistance sufficient to accommodate the cylindrical portion of member 12of the projectile. The rear end of the grain is in the form of acircular face 21.

At the forward conical surface of the grain and at a position outside ofprojectile member 21, there is an annular groove 23 for reception of anigniter ring 24. The annular groove 23 interconnects the perforations ofthe grain which are near the outer circumference of the grain.

Extending rearwardly from the forward end of the grain, there are aplurality of separated cylindrical perforations 25 parallel to eachother and to the longitudinal axis of the grain. These perforationsextend almost but not quite to the rear face 21 of the grain, atpositions 26, which can be for example, about one-. fourth inch from therear of the grain. Grain sizes will of course vary with gun and bulletsizes. It will be seen from FIG. 2, that there are 61 of theperforations in the particular grain illustrated. It will be understood,however, that a greater or a lesser number may be provided as may appearbest from such considerations as dimensions. FIG. 1, for the purpose ofclarity, does not indicate this many perforations.

The outer circumference and the rear end of face 21 v of the grain arecovered by a restrictive layer or coating 27 of a material whichinhibits burning on these surfaces.

The solid grain 1 8 can be fabricated by casting, molding or extrusiontechniques from any propellant substance compatible with a gunmechanism, for example a double base (nitro-cellulose-nitroglycerin),triple base, or a composite, in the proper formulation for a desiredrapidity of burning, in the form of a slurry which, after fabrication,will solidify to form the solid grain with its perforations. Thematerial for igniter 24 can be a pyrotechnic such as black powder.Theexternal restriction layer 27 can be a coating of a burning inhibitorsuch as cellulose acetate ordinarily applied by dipping the solid grainin the liquid form of the restrictive material.

In the use of this caseless ammunition, ignition will be accomplished inthe usual way which will initiate the burning of the grain at theopenings of the perforations at the front of the grain and burnrearwardly down through the perforations. The burning in theperforations will occur at all of the perforations substantiallysimultaneously inasmuch as the hot gases from the initial ignitionimmediately travel into all of the perforations. Thus all of theperforations burn on all of their internal cylindrical surfaces, andthis burning progresses in all radial directions in reference to thelongitudinal axis of each perforation. Burning will not occur along therestrictive surfaces due to the restrictive coating 27.

By reason of this arrangement, there is a pressure gradient at the frontof the grain which while propelling the projectile forwardly through thegun barrel, exerts pressure on the grain rearwardly in its chamber, thusinsuring immediate separation of the projectile from the grain, andpreventing the grain from following the projectile down the gun barrel.This has the great advantage of eliminating the mass of the grain as anypart of the material projected forwardly.

FIG. 3 shows another embodiment of this invention in which theprojectile 30 is fully telescoped by the propellant grain 31 in the formof a cylinder of solid propellant and having a plurality of separatedcylindrical perforations 32 parallel to each other and to thelongitudinal axis of the grain extending from the forward part of thegrain almost to the rear face of the grain, in the manner alreadydescribed in connection with FIG. 1.

It will be understood that the cross-section of this grain as well asall other grains described herein is circular, and that the number ofthe parallel perforations can be about the same as that of FIGS. 1 and2. This grain, like all other grains described herein carries therestrictive coating 27 on its outer surfaces, as in FIG. 1.

In this instance of a fully telescoped projectile it is desirable thatthe forward end of the grain taper outwardly at 33 toward the periphery,rather than tapering inwardly as shown in FIG. 1.

The projectile, such as a bullet, has a head 34 fitted to a rear portion35. A plug 36 fitted centrally into the rear portion of the projectilehas a chamber 37 containing an expulsion charge 37a for initiating theexpulsion of the projectile from its telescoped position within thepropellant grain. The charge 37a will be selected as one which burnssufficiently rapidly to perform this expulsion function. The chamber 37is vented rearwardly through a nozzle 39.

For the purpose of igniting the expulsion charge 37a, there is provideda combustible booster charge 38 extending from the rear of nozzle 39 tomeet a combustible primer 40 at the rear face of the propellant grain.The primer charge is a type capable of being ignited by a firing pin inthe breech block of the gun.

Ignition of primer 40 ignites the booster charge 38 which in turnignites the expulsion charge 370. Ignition of the propellant grain 31 isachieved by the hot gases from the vented chamber 37 after theprojectile has been expelled from the propellant grain due to the highpressure developed in chamber 37 by combustion of expulsion charge 37a.The gases vent from the relatively high pressure chamber 37 through thenozzle to the relatively lower pressure chamber formed by the cavity inthe propellant grain created at the rear of the projectile when theprojectile starts to be expelled from the grain. The main thrust of theprojectile forwardly through the gun barrel is due to the burning of thegrain in the manner described in connection with FIGS. 1 and 2.

In the embodiment of FIG. 4 the rear portion 41 of the projectile 42 isprovided with a frusto-conical plug 44 flaring outwardly toward the rearand providing two orifices 44. An expulsion charge 45 is set into thisplug and behind the expulsion charge there is placed a percussion primer46 held in position in the plug by a washer 47 having a central openingwhich communicates with an axially located cylindrical opening 48 whichextends through to the rear portion of the grain 49. A push rod 50within opening 48 has a firing pin 51 at its forward end so that whenthe push rod is actuated forwardly the pin strikes and ignites thepercussion primer to ignite the expulsion charge where high pressuregases are developed which vent through orifices 44 to expel theprojectile from within the grain, and ignite the grain in the mannerdescribed in connection with FIG. 3.

The embodiment of FIG. 5 is somewhat similar to that of FIG. 3 butdiffers in that instead of having the booster charge 38 as in FIG. 3,there is provided the push rod 50 in the cylinder 48, having the firingpin 51 as in FIG. 4 actuable against a combustible primer 52 which inturn ignites a booster charge 53 held in the plug, from which the hotgases are vented through the nozzle to ignite the grain as theprojectile moves forwardly from the grain. The push rod serves as aclosure for cylinder 48.

In the embodiments of FIGS. 6, 7 and 8, booster charges are provided inthe propellant grain behind the projectile, providing for both expulsionof the projectile and ignition of the propellant grain.

In the construction of FIG. 6, there is a push rod 54 slidable in therear cylinder of the grain, the interior of which contains the boostercharge 55 ignitable by a stab primer 56 located at its forward end,ignition of which is initiated when the primer is stabbed by a firingpin 57 fixed at the rear of the projectile such that forward movement ofthe push rod initiated the ignition.

In the embodiment of FIG. 7, a combustible primer 40 is located at therear of the grain as in FIG. 3 which when ignited flashes through thetubular opening 58 through the grain, communicating with booster charge59 behind the projectile which is telescoped within the grain.

In the structure of FIG. 8, only the rear portion of the projectile isheld within the grain, the rear end of which is provided with acombustible primer 40 communicating with combustible booster material 60placed in a tubular portion 61 extending from the primer forwardly to aposition near the rear of the projectile at which place the tube orhollow 60 enlarged to a larger diameter at 62, which also containsbooster material at the rear of the projectile.

The use of a propellant grain according to the present inventionpossesses many advantages over prior known grains for this purpose,among which are the following: Increased velocities of the projectilewith reduced pressures; greater performance reproducibility; lessexpensive production techniques; and reduced heat transfer from thegrain to the gun chamber wall. In addition, the arrangement permitscomplete tailoring of a gun propulsion system; and increases reliabilityand durability of breech obturation; and provides for corrections forlot-to-lot variability.

It will be recognized that the invention is not limited to theparticular configurations shown in the drawings and description, whichare given by way of illustration rather than of limitation.Modifications within the scope of the invention will suggest themselves.For example, the perforations need not be of circular crosssection, andfurthermore need not be cylindrical. Instead, perforations which taperoutwardly toward the forward end of the grain may be employed ifdesired. This will result in exertion of even greater back pressure onthe grain, insuring separation of projectile from grain.

What is claimed is:

1. A solid propellant structure suitable for propelling a projectile outof a gun chamber forwardly through a gun barrel, said propellantstructure comprising an elongated, solid propellant grain of circularcross section having a rear end and an inwardly tapered forward end,said forward end being adjacent the projectile, said grain upon burningacting to propel the projectile forwardly and away from the forward endof the grain, said grain having a longitudinal axis along which theprojectile is to be set, a plurality of radially -positionedperforations extending rearwardly from the forward end of the grain in alongitudinal direction parallel to said longitudinal axis through themajor length of the grain and terminating short of the rear end thereof,and means comprising an igniter ring positioned on the tapered forwardend of the propellant grain for igniting the grain at the forward endthereof to initiate burning within said longitudinal-extendingperforations to produce gases of combustion, said manner of ignition andburning serving to constrain movement of the propellant grain while theprojectile is propelled in a forward direction, said propellantstructure having no metal casing thereabout and further characterized inbeing wholly combustible 2. A grain according to claim 1 in which theouter circumferential surface of the grain has a coating of a materialwhich inhibits burning.

3. A grain according to claim 1 in which the grain is a casting from aslurry comprising a double base of nitrocellulose and nitroglycerin.

4. A grain according to claim 1 in which the grain has an outercircumferential surface which is cylindrical and the perforations havecross-sections which are circular.

5. A grain according to claim 1 in which a projectile is attached to thegrain with at least part of the projectile extending in front of thegrain.

6. A grain according to claim 1 in which a projectile is telescopedwithin the front part of the grain.

k II

2. A grain according to claim 1 in which the outer circumferentialsurface of the grain has a coating of a material which inhibits burning.3. A grain according to claim 1 in which the grain is a casting from aslurry comprising a double base of nitrocellulose and nitroglycerin. 4.A grain according to claim 1 in which the grain has an outercircumferential surface which is cylindrical and the perforations havecross-sections which are circular.
 5. A grain according to claim 1 inwhich a projectile is attached to the grain with at least part of theprojectile extending in front of the grain.
 6. A grain according toclaim 1 in which a projectile is telescoped within the front part of thegrain.